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Article Title

Analytical methods for the determination of acifluorfen and bentazone residues in crops

Abstract

Methods using high performance liquid chromatography (HPLC) were developed to determine acifluorfen and bentazone in crops. Twenty samples of dry bean crops and rice were purchased from traditional markets and analyzed. Acifluorfen and bentazone being weak acids, were selectively extracted as ion pair compounds formed with tetrabutylammonium ion into dichloromethane under basic conditions. This technique was used for cleanup prior to determination of acifluorfen and bentazone by reverse phase liquid chromatography with UV detector. A residue of aciflourfen was extracted from crops with acetonitrile and acetonitrile-H2O (9:1, v/v) and a residue of bentazone was extracted from crops with acetone. The extracts were evaporated to dryness, dissolved in pH 8.0 phosphate buffer, and washed with n-hexane and dichloromethane. Ion pair compounds were formed by adding tetrabutylammonium ion into an aqueous phase, and then extracted into dichloromethane. The dichloromethane phase was evaporated and the residues were dissolved in organic solvent and determined by HPLC. Recovery studies were carried out by spiking the standards of acifluorfen and bentazone at the levels of 0.05-0.15 and 0.25-0.75 ppm, respectively. The average recoveries were determined to be 91.6-97.6% and 88.6-91.7%, respectively. The detection limits in crops were 0.02 and 0.05 ppm for acifluorfen and bentazone, respectively. No residues of acifluorfen or bentazone were detected in dry bean crop samples, nor was bentazone residue found in rice samples.

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